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BBC 781 heads

Discussion in 'The Garage' started by 77crewcab, Apr 7, 2005.

  1. 77crewcab

    77crewcab 1/2 ton status

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    Just popped the valve covers on my 454 for the first time and found that the head are a 336781 casting for passenger cars from '74. The engine came from a 74 Chevelle/Monte Carlo. Just wondering if these are a good (desirable) head for a truck or not. On a side note I found the rockers were almost all loose and the front rocker on the passenger side was not even on the spring and has a very bent pushrod and broken valve guide. So looks like I have some work to do but at least there was ZERO sludge built up, they are very clean which was surprising.
     
  2. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    The 781's are a large chamber (119cc) oval port head, from the factory they will have the 2.06 int & 1.88 exh valves. IMO, these are wonderful heads for any bbc. They do flow more than the later model peanut port heads but not so much that they will hurt the bottom end performance, just good all purpose castings.

    FWIW, I have 2 sets myself.
     
  3. 77crewcab

    77crewcab 1/2 ton status

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    Sounds good. Please refresh my memory on how to tighten the rockers.
     
  4. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Man, I suck at rocker adjustment...

    The short description is - from a loose starting point, tighten the nuts until the rocker stop tapping and then tighten 1/4 turn more.

    I always hated this because with the engine running I always have trouble localizing which is still making noise and which isn't. I'm too impatient.
     
  5. 77crewcab

    77crewcab 1/2 ton status

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    So it is supposed to be done with the motor running? Ive always seen it donewith the motor off.
     
  6. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    This is the part where I suck.

    There is a method where the rockers are adjusted based on the amount of resistance the rocker applies to the pushrod (felt when twisting the pushrod). It's an aquired "feel" that I have not had enough engine building experience to learn.

    Of course, all of this (including my last post) applies to regular old flat tappet hydraulic lifter set ups. Solid lift stuff can be done by feeler gauge.
     
  7. 77crewcab

    77crewcab 1/2 ton status

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    Thanks that helps a lot.
     

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